Ballast apparatus for operating a pair of gaseous discharge lamps

ABSTRACT

A ballast apparatus for sequentially igniting and operating two gaseous discharge lamps includes a transformer having a primary winding with a tap dividing it into two primary winding portions. A first secondary winding is connected to the end of one primary winding portion remote from the tap. A second secondary winding is connected to the first secondary winding and a first lamp can be connected between the second secondary winding and the primary winding tap. A capacitive reactance is connected to the first secondary winding and a second lamp can be connected between the capacitive reactance and the primary winding tap.

United States Patent [191 Neusbaum [451 May8, 1973 [54] BALLAST APPARATUS FOR OPERATING A PAIR OF GASEOUS DISCHARGE LAMPS Primary Examiner-Palmer C. DeMeo Att0rney.l0hn M. Stoudt et al.

[57] ABSTRACT A ballast apparatus for sequentially igniting and operating two gaseous discharge lamps includes a transformer having a primary winding with a tap dividing it into two primary winding portions. A first secondary winding is connected to the end of one primary winding portion remote from the tap. A second secondary winding is connected to the first secondary winding and a first lamp can be connected between the second secondary winding and the primary winding tap. A capacitive reactance is connected to the first secondary winding and a second lamp can be connected between the capacitive reactance and the primary winding tap.

Inventor: Frank A. Neusbaum, Danville, 111.

[7 3] Assignee: General Electric Company, Fort Wayne, Ind.

[22] Filed: Mar. 13, 1972 [2]] Appl. No.: 234,176

[52] US. Cl ..315/257, 3l5/D1G. 5, 315/323 [51] Int. Cl ..H05b 41/16 [58} Field of Search ..3I5/l38, 257, 323,

3l5/D1G. 5

[56] References Cited UNITED STATES PATENTS 2,558,293 6/l95l Feinberg ..315/138 X 2,683,243 7/1954 Feinberg ..315/138 2,682,014 6/1954 Feinberg ...315/l38 2,788,469 4/1957 Feinberg ..3l5/l38 BALLAST APPARATUS FOR OPERATING A PAIR OF GASEOUS DISCHARGE LAMPS BACKGROUND OF THE INVENTION This invention relates to ballast apparatus for starting and operating gaseous discharge devices such as fluorescent lamps. More particularly, it relates to such a ballast apparatus for sequentially igniting and controlling the current to a pair of lamps connected in series circuit relation with each other.

US. Pat. No. 2,965,808, issued of Dec. 20, 1960 to Daniel Lovinger and assigned to General Electric Company, assignee of the present invention, sets forth a ballast apparatus for series sequence operation of a pair of lamps from an elevated voltage source, using a ballast design which also is suitable for use with normal residential or commercial distribution voltages. That apparatus utilizes ballast designs with three secondary windings. Economic advantages would result from the use of a two secondary winding ballast for such applications as the material and labor associated with the third secondary winding would be eliminated.

Difficulty has arisen in the past with such two secondary winding designs as the voltages between various parts of the system can become much higher than the supply voltage; sometimes they can be more than twice the supply voltage. Such high voltages require the use of electric conductor with insulation which will withstand the higher level voltages. The voltage applied to a conductor should not exceed the voltage rating of the conductor by more than about percent. At the present time generally available insulations economically feasible for use in such devices have voltage ratings of no more than about 1000 volts. Thus the highest voltage in such a system should not exceed about 1 100 volts under any circumstance. This becomes a limiting factor particularly when such a ballast apparatus is to ignite and operate lamps from a 480 volt distribution system such as is found in many industrial locations.

Also the open circuit voltage across the lamp holders should be kept as low as practicable since this is the voltage across the lamp holders when a user can fairly easily come into contact with the lamp holder contacts.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved ballast apparatus of the series sequence type.

It is another object of the invention to provide such an improved ballast apparatus which has relatively low voltages associated with it.

It is yet another object of the invention to provide such an improved ballast apparatus which utilizes only two secondary windings.

In carrying out the invention in one form thereof there is provided a ballast apparatus for sequentially initiating and operating a pair of gaseous discharge lamps, including a transformer having a primary winding with a tap dividing it into two primary winding portions. A first secondary winding has one end connected to the end of one primary winding portion remote from the tap. A second secondary winding has one of its ends connected to the other end of the first secondary winding. There is provided means for connecting a first lamp between the other end of the second secondary BRIEF DESCRIPTION OF THE DRAWING The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the 0 concluding portion of the specification. The invention itself, however, together with further objects and advantages thereof, may be better understood by reference to the following description taken in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic electric circuit diagram of a ballast apparatus incorporating one form'of the present invention; and

FIG. 2 is a somewhat simplified plan view of a high reactance ballast transformer for use in the ballast apparatus of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawing there is shown a ballast apparatus for sequentially initiating and operating a pair of gaseous discharge lamps in accordance with one embodiment of the present invention. Referring particularly to FIG. 2 there is shown a high leakage reactance transformer 10 useful in the ballast apparatus. The transformer 10 includes a center winding leg 11 supported in and carried by an outer enclosing yoke 12. A number of windings, including a primary winding 13, a first secondary winding 14 and a second secondary winding 15, are independently formed on the center leg in spaced apart relationship so that the secondary windings are in inductive relationship with the primary winding. Both the first and the second secondary windings are loosely coupled with the primary, due to their being spaced apart from the primary and in addition, if desired, by reason of magnetic shunts l6 and 17 in the magnetic circuits for the secondary windings. Thus both of the secondary windings l4, l5 constitute high leakage reactance windings in the transformer. However, the first secondary I4 is more loosely coupled to the primary than the second secondary 15 as indicated by the shunt 16 being larger than the shunt 17. The first secondary winding I4 is connected in the opposite electrical direction to the primary winding 13 in order to provide a voltage which is bucking or opposing the voltage of the primary winding while the second secondary winding 15 is connected in the same electrical direction as the primary winding to provide an additive voltage with respect to the primary winding voltage.

Referring now particularly to FIG. 1, there is shown a schematic electrical circuit diagram of a ballast apparatus incorporating one embodiment of the present invention. The apparatus may be provided with electric energy from a suitable source such as a 480 volt source often found in industrial applications through supply conductors 20 and 22. The primary winding 13 is connected between the supply conductors 20, 22 and is divided. into two primary winding portions 13a and 13b by a center tap generally indicated at 24. More specifically, the distal end of winding portion 13a is connected to supply conductor 20 while its inner end is connected to a tap conductor 26. The inner end of prirnary winding portion 13!; is connected to a tap conductor 28 and its distal is connected to supply conductor 22. The tap conductors 26 and together from the center tap 24. The use of two tap conductors 26, 28 enables a pair of disconnect latnp holders to be utilized with the ballast. However, as will be explained in more detail below, it will be understood that the conductors 26, 28 are normally interconnected and at the same potential. Thus, if lamp holders other than disconnect larnp holders are to be used, the center tap 24 may be provided by a single conductor.

One end of the first secondary winding 14, which may also be called the start winding, is connected to the distal end of the primar winding portion 13b. One end of the second secondary windingl S, which may also be called the run winding, is connected to the other end of the start winding 14. The other end of second secondary or run winding is connected to a first gaseous discharge device such as fluorescent larn p generally indicated at 30, as indicated-by conductor 31. One side of a capacitive reactance 32 is connected to the start .winding 14 while its other side is connected to a second fluorescent lamp 3 4, as indicated by conductor 33.

Capacitive reactance 32 is bridged by a bleed resistance 38. The tap conductor 28 is connected to the other side of fluorescent lamp 30 while the tap conductor 26 is connectedto the other side "of fluorescent lamp'34. Additionally a conductor 36 interconnects the left end (asseen in FIG. '1) of the lamps30, 34. The additive relationship of secondary winding 15 and the bucking relationship of secondary winding 14 with respect to the primary winding 13 is illustrated by the plus. and minus signs shown adjacent each of the windings.

While the lamps 30, 34 are schematically shown with their terminals directly connected to-the conductors 26, 28, 31, .33 and 36 it will be understood that this is for illustrative purposes. Normally these conductors are connectedto fluorescent lamp holders which receive the terminals of the fluorescent lamps, as it well known in. the art. More specifically coniluctor's 28 and 36 can be connected to one disconnect lampholder while conductors 26 and 36 are connected to a second disconnect lamp holder. As is well known, with disconnect lampholders the conductors 26, 36 and 2 8, 36 will be interconnected only when a *lanip terminal is received in the associated lamp holder. Thus a circuit is completedfrom primary winding portion 13a through conductors 26, 36 and 28 to primary winding portion 13b only if both lamps 30 and 34 are mounted in the disconnect lamp holders. This assures that a complete electrical path through the primary winding is available only if both lamps are in place.

Assume for purposes of illustration that the ballast apparatus'is intended to operate a pair of lamps from a 480 volt, 60 hertz supply and that the lamps are of the commercially available type that require about 625 volts for ignition. The primary winding may be divided by center tap 24 so that 3o0 volts will appear across primary winding portion 13a and 120 volts will appear across primary winding portion l3b.'Start winding 14 may be constructed so that its open circuit induced voltage is approximately 765 volts while run winding 15 is constructed so that its open circuit induced voltage is approximately 470 volts rent through the lamp almost immediately rises to about 135 'miliamps. The current through lamp- 34 tion 13!), start winding 14 and capacitivereactance 32.

Initially no current flows through eitherof the lamps as they are off. Lamp has impressed across it the eumulative voltage around the loop including primary winding portion 13b, start winding 14 and run winding 15. Prirnary winding portion 13b and run winding 15 are additive and of the opposite polarity to start winding 14 so that, with the nominalyalues setforth above, about 175 volts, appears across the terminals ofthe lamp 30'. This is not sufficient to ignite it. Lamp 34has' flows through the loop, including primary winding por- Since the start windin 14 has more inductive reactance than the value of capacitive reactance 32, thecurrent is lagging and causes a phase-shift in the voltage of start winding 14. Because of the phase shift of the startwinding l4 voltage, the lamp 30 now will have a higher-voltage, in the order-'fof 725 volts impressed across it and it will be ignited. Once both lamps ignite the lamps are operated in a loop which includes the lamp 30, the run coil 15, the capacitive reactance 32, the lamp 34 and the conductor'36. Because of the very high value of the inductive reactance of the start winding l4l very little lamp operating current will few other than in the operating loop. I V w A ballast apparatus such as that illustrated in FIG. -1 was designed and built to 'o crate a pair of fluorescent lampsfroma 480 volt 60 hertzsource. In that ballast the primary winding 13 consisted of 1400 turns of 0.0142 inch diameter conductor, the first secondary or start winding 14 consisted of 239.0 turns of 0.008 inch diameter electric conductor, thesecond secondary or p winding is consisled of 1764 mmsofoo zs inch diameter electric conductor, the capacitive reactance 32 had a value of 2.0 microfarads, and the discharge resistor 38 was 2 meg ohms..The primary winding 13 was tapped so as to provide a 3 to, 1 ratio between primary winding portion 13a and primary winding portion 13b. The various windings were designedto have the nominal open circuit voltages previously described.

With such an exemplification ballast a paratus, the voltages between various points inthe apparatus andits leads were held to a minimum consistent with that required for starting and operating the lamps. Also the open circuit voltages across the lamps, which would be across the lamp holders in the event someone accidently touched them, were limited to the approximately .645 and approximately volts discussed previously in the description of the operation in the circuit. Additionally all the voltages were maintained below 1100 volts. The highest voltage which was'measured was between the cohductor 20 andthe conductor 31 when larnp 34 was conducting and before lamp 30 begin to conduct. While this was about 1000 volts it will be understood that normally such a voltage exists only momentarily as the lamps 34, 30 light in sequence very quickly.

By contrast somewhat similar ballast apparatus with essentially similar components but with one end of the start winding 14 connected to the center tap 24, the run winding 15 and capacitive reactance 32 connected to the other end of the start winding 14 and the lamps connected between the winding 15 capacitor 32 and the supply conductor 22 have been constructed and operated. A much less favorable situation exists with such ballast apparatus. For instance the voltage between the lamp side of the capacitive reactance and the supply conductor 20, with the lamps off, is nominally l 125 volts. Such a voltage can be present for long periods of time as it occurs when the lamps are off.

While in accordance with the patents statutes, there has been described what at present is considered to be the preferred embodiments of the invention, it will be obvious to those skilled in the art that various modifications may be made therein without departing from the invention. it is intended, therefore, in the appended the claims to cover all such modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. A ballast apparatus for sequentially initiating and operating a pair of gaseous discharge lamps, including: a transformer having a primary winding including a tap dividing it into two primary winding portions; a first secondary winding connected to the end of one of said primary winding portions remote from said tap; a second secondary winding having one of its ends connected to the other end of said first secondary winding; means for connecting a first lamp between the other end of said second secondary winding and said tap; a capacitive reactance connected to said other end of said first secondary winding; and means for connecting a second lamp between the other end of said capacitive reactance and said tap.

2. A ballast apparatus as set forth on claim 1 wherein said first secondary winding is in voltage bucking relationship to said primary winding and said second secondary winding is in voltage additive relationship to said primary winding.

3. A ballast apparatus as set forth in claim 1 wherein each of said first and second secondary windings is loosely coupled to said primary winding, said first secondary winding being more loosely coupled to said primary winding than said second secondary winding.

4. A ballast apparatus as set forth in claim 1 wherein said tap divides said primary winding into a first portion having a relatively large number of turns and a second portion having a relatively small number of turns; said first secondary winding being connected to said second portion of said primary winding. 

1. A ballast apparatus for sequentially initiating and operating a pair of gaseous discharge lamps, including: a transformer having a primary winding including a tap dividing it into two primary winding portions; a first secondary winding connected to the end of one of said primary winding portions remote from said tap; a second secondary winding having one of its ends connected to the other end of said first secondary winding; means for connecting a first lamp between the other end of said second secondary winding and said tap; a capacitive reactance connected to said other end of said first secondary winding; and means for connecting a second lamp between the other end of said capacitive reactance and said tap.
 2. A ballast apparatus as set forth on claim 1 wherein said first secondary winding is in voltage bucking relationship to said primary winding and said second secondary winding is in voltage additive relationship to said primary winding.
 3. A ballast apparatus as set forth in claim 1 wherein each of said first and second secondary windings is loosely coupled to said primary winding, said first secondary winding being more loosely coupled to said primary winding than said second secondary winding.
 4. A ballast apparatus as set forth in claim 1 wherein said tap divides said primary winding into a first portion having a relatively large number of turns and a second portion having a relatively small number of turns; said first secondary winding being connected to said second portion of said primary winding. 